1. Field of the Invention
The present invention relates to a curable composition. In particular, the present invention relates to a curable composition, which is suitable for use as the packaging material of electronic components such as light emitting diodes.
2. Descriptions of the Related Art
Organic resin, due to its properties of high processability, light weight, low cost and impact resistance etc., has gradually replaced inorganic glass for use as optical components such as optical lens and packaging materials of electronic components. Recently, due to the development of light emitting diode techniques (e.g., high brightness, multiple color property etc.), organic silicon resins which have better heat resistance, water resistance and transparency, have gradually replaced epoxy resins for use as the packaging material of electronic components.
An organic silicon resin, such as organopolysiloxane, can be cured through alkylation with silicon hydrides. The cured solid product of the alkylation has a high refractive index and transmittance, and can be used as the packaging material of a light emitting diode. For example, JP H8-176447 discloses a curable organopolysiloxane composition, comprising an organopolysiloxane in which each molecule has a silicon-bonded phenyl group and an silicon-bonded alkenyl group, an organic hydrogen siloxane, and an alkylation catalyst; and JP 2003-128922 discloses a curable organopolysiloxane composition, comprising an organopolysiloxane in which each molecule has at least two silicon-bonded alkenyl groups and a silicon-bonded phenyl group, an organopolysiloxane in which each molecule has at least two silicon-bonded H, and an alkylation catalyst. Such curable organopolysiloxane compositions, due to their high viscosities, have disadvantages including operation difficulty and poor adhesive property to the substrate.
U.S. Pat. No. 7,527,871 B2 discloses a modified curable organopolysiloxane composition, in comparison to the above prior arts, which comprises a component of a linear organopolysiloxane with at least two silicon-bonded alkenyl groups and at least one aryl group and thus, can provide a cured product with a low viscosity and well adhesive property. However, during the synthesis of the above component, a great amount of nonreactive residue of methyl phenyl rings is inevitably generated for the reaction equilibrium, which will make the surface of the cured product obtained from the composition sticky. In addition, any procedure used to remove the rings, such as a high-temperature distillation, will probably lead to the breakage of the bonding between the phenyl groups and result in the appearance of yellowing. Furthermore, since the added component is a linear organopolysiloxane with insufficient strength, the cured product will tend to fracture under a high temperature or a drastic temperature variation.
In view of the above, the present invention provides a curable composition without any undesired residue of rings during the manufacturing process. The cured product of the composition has outstanding heat resistance, transmittance as well as refractive index, and the yellowing barely occurs during the high temperature curing process of the composition. In addition, the ratio or structure of the components contained in the curable composition can be adjusted to satisfy the demands of a quick curing process and to provide the desired properties including superior transmittance, thermal resistance and surface conditions.